The structure of tandem chromosomal duplications of the tryptophan operon will be studied in S. typhimurium. Factors which affect the stability of the duplications will be studied including the effects of interactions of mutant supX, recA, recB and recC alleles with temperature, UV and photo reactivating light. Studies of the effects of chromosomal insertions on the cotransduction linkage of nearby markers will be used to further characterize the process of viral encapsulation of host cell DNA. The bacterial growth inhibiting effects of normal metabolites such as indole and riboflavin will be analyzed.